interface Com{
  int add(int a, int b);
}
abstract class A{
  abstract int add(int a, int b);
}
class B extends A implements Com{
  public int add(int a, int b){
      return a+b;
  }
}
public class xiti6_2{
  public static void main(String args[]) {
    B b = new B();
    Com com = b;
    System.out.println(com.add(12,6));
    A a = b;
    System.out.println(a.add(10,5));
  }
}
